Helsinki Institute for Information This document defines extensions to provide Packet Level Authentication (PLA) functionality for the HIP protocol. PLA provides strong hop-by-hop security features that allow intermediate nodes to detect the hostile traffic quickly, and drop the traffic before it reaches the destination and can consume resources in the target network. Unlikely other similar solutions, PLA does not require excessive signaling or state in verifying nodes, and is path-independent, making it suitable for dynamic environments, such as ad-hoc networks.